In particular, the invention relates to apparatus for glueing inner books. When reference is made in the context of this invention to a “book” or an “inner book” the terms shall be understood to mean that substrate in which one or several leaves or pages of a material that can be written upon, for example paper or films, are joined with an adhesive bond to a binding made, for example, of paper, cardboard or film. In particular, the term includes books in the conventional sense, as well as bound magazines, catalogs and the like.
Conventionally, an adhesive bond is used to bind material written upon and its binding or cover. The adhesive is often applied directly onto the spine of the book or onto the side of the inner book by means of roller applicator systems. However, one unwanted effect produced in many cases is that the adhesive is not applied uniformly and that the adhesive is squeezed out at the edges of the inner book when the applicator rollers compress the inner book. Moreover, in the roller trough of the roller applicator systems, bubbles are often produced in the adhesive, leading to foaming of the adhesive and to high costs for cleaning.
Attempts have also been made to apply the adhesive to an inner book through spray nozzles. This method, too, results in the uniformity of adhesive application often being unsatisfactory. Another frequent occurrence is local swelling of the book sides and thickening caused by droplets of adhesive, with the result that spines become rounded and the stacking of books is hampered. In addition, a significant portion of the adhesive or its solvent evaporates on spray application, leading to persistent contamination of a bookbinding workplace with chemicals that are damaging to health.
An apparatus for glueing inner books is known from U.S. Pat. No. 5,271,794 (the '794 patent) which comprises slot nozzles for applying adhesive to opposite sides of an inner book. The slot nozzles disclosed in the '794 patent are designed to contact the spine to be coated. When using the slot nozzles proposed in the '794 patent, adhesive can only be applied with the same width at all times (viewed transversely to the principal direction of movement of the inner books to be glued).
The object of the present invention was therefore to provide an apparatus for applying fluid onto a substrate, with which the disadvantages described in the foregoing can be mitigated or entirely avoided.